1. Field of the Invention
The present invention concerns printing machines in general and in particular the situation in which the objects to be printed are presented in a stack.
This is the case with compact discs, for example.
2. Description of the Prior Art
The present invention is more precisely directed to the situation in which, for automatically feeding the printing machine with objects to be printed, a loader is used including a presentation device which is adapted to convey to a loading station at least one stack support carrying a stack of objects to be printed, a lifting device operative at the loading station and adapted to take up a stack of objects from below and to raise it stepwise as objects are removed from it, and a transfer device operative between the loading station and the printing machine and adapted to take an object from the stack at the loading station and then to convey this object to the printing machine, the transfer device being provided for this purpose with a take-up unit and being reciprocated vertically during each take-up cycle so that it can take up an object on the underlying stack.
For the system to operate correctly the loader is always controlled in synchronism with the printing machine.
Accordingly, at present the printing machine ceases to be fed with objects to be printed each time that the stack is changed, and for as long as it takes the presentation device to withdraw from the loading station the stack support which has just been emptied and to substitute for it a new stack support carrying a new stack of objects to be printed. This is detrimental to the productivity of the printing machine.
A general object of the present invention is an arrangement for masking the consequences of the inevitable changing of stack supports.